[108] Verses 16-19 are parenthetic, and either an address to Muhammad by Gabriel desiring him (I) not to be overcome by any fear of being unable to follow and retain the revelation of this particular Sura; (2) or, not to interrupt him, but to await the completion of the entire revelation before he should proceed to its public recital. In either case we are led to the conclusion that, from the first, Muhammad had formed the plan of promulging a written book. Comp. Sura xx. 112.